1. Field of the Invention
This invention relates to wire for use in making electrical connection between plural locations and, more specifically, to a gold-metal alloy or metal filled composite gold wire and preferably silver-gold (Ag--Au) alloy wire, generally for use in the fabrication of semiconductor devices.
2. Brief Description of the Prior Art
The wiring of choice for use in the fabrication of semiconductor devices has generally been gold of controlled purity. By controlled purity it is meant that the gold has additives in parts per million (i.e., generally much less than one percent and further generally much less than 0.1 percent) to provide additional strength, yet retain good bondability to pads on semiconductor chips and lead frames, malleability and forming properties. The small differences in additives in parts per million can and often do make large differences in the hardness of the gold wire as well as in its other physical properties. To run a wire and form a ball bond therewith during semiconductor fabrication, it is highly desirable to have a readily malleable, easily formed alloy of gold. Materials other than gold have been used for electrical interconnection in semiconductor devices, these materials generally being aluminum and copper, though other base metals can also be used, however these base metals as well as other noble metals have not proven to provide as satisfactory results as gold.
The prior art gold wiring as described above provides excellent electrical interconnection, malleability and bondability and is therefore highly desirable for the properties it provides, however gold is very costly. As a factor in the constant attempt at cost reduction in the fabrication of semiconductor devices, the cost of wiring must be considered. The prior art cost reduction attempts have utilized materials other than gold and have generally not proven to be highly satisfactory, this being the principal reason for gold of controlled purity being the interconnect wiring material of choice.